Reduction of co and nox in full burn regenerator flue gas

ABSTRACT

A hot oxygen stream containing radicals is fed into a gas stream, such as a catalyst regenerator flue gas stream, that contains carbon monoxide to convert carbon monoxide to carbon dioxide.

FIELD OF THE INVENTION

This invention relates to treatment of gas streams such as flue gasesfrom catalyst regeneration units.

BACKGROUND OF THE INVENTION

Fluidized catalytic cracking (FCC) is a unit operation in whichpetroleum fractions of higher molecular weight are cracked into smallermolecules under heat and with a catalyst. During the cracking process,coke deposits form on the surface of the catalyst, necessitatingregeneration of the catalyst. Therefore, the catalyst is continuouslyseparated from the vapors generated by the cracking process andregenerated in a FCC regenerator where the coke deposits are burned offand the catalyst activity is restored.

The FCC regenerator can operate in two modes: full burn and partialburn. In the full burn mode, most of the carbon in the coke deposits isconverted to CO₂ by reacting with oxygen in the oxidant stream that isalso fed to the regenerator. When the regenerator is operated in thepartial burn mode, the carbon reacts with oxygen in the oxidant streamand is converted to both CO and CO₂. In this instance, the CO in theregenerator flue gas is typically oxidized to CO₂ in a downstream boilerto recover heat from the CO oxidation and also to limit emissions of COin the boiler flue gas. The CO boiler has air fired burners to create ahot flame zone that the regenerator flue gas has to pass through inwhich the CO is oxidized to CO₂. Refinery off-gas can be used asauxiliary fuel for the CO boiler burners. The heat released by theoxidation of CO and by the combustion of the refinery gas is recoveredin the boiler to produce process steam.

The FCC regenerator flue gas also contains other species such as SO₂ andNOx. Typically, in the full burn mode some of the nitrogen in the carbondeposits is oxidized to NOx.

Some FCC systems have low temperature NOx and/or NOx/SOx removaldevices. The low temperature NOx removal process normally requires aspecified amount of gas residence time for achieving the desired NOxreduction efficiency. One problem associated with the FCC capacityincrease is that the volume of the FCC regenerator flue gas may alsoincrease. The increase of the regenerator flue gas volume shortens thegas residence time available for the downstream NOx removal devices andreduces their NOx reduction efficiency. The increase in the regeneratorflue gas volume also promotes carryover of corrosive scrubbing fluid andincreases the risk of accelerated corrosion after the scrubber.

Other processes that treat FCC regenerator flue gas differ from thepresent invention, but differ in significant conditions and do notprovide the advantages that the present invention achieves. Forinstance, U.S. Pat. No. 5,240,690 teaches adding oxygen-containing gasto regenerator flue gas to produce an off gas having a temperaturebetween 1000 F and 1600 F, but states that the objective is to increasethe formation of NOx in the flue gas. U.S. Pat. No. 5,716,514 disclosesa method in which carbon monoxide is preferentially not converted tocarbon dioxide. U.S. Pat. No. 5,830,346 discloses a method that requiresuse of a catalyst for the conversion.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, a method for treating a regenerator fluegas stream comprises

(A) providing from a catalyst regenerator a regenerator flue gas streamthat contains carbon monoxide in a concentration less than 10,000 ppmand contains NOx in an amount up to 1,000 ppm;

(B) mixing fuel and oxygen and combusting a portion of the oxygen in themixture with said fuel in a chamber to form a hot oxidant streamemerging from said chamber that contains oxygen, wherein the residencetime of said combustion in said chamber is long enough that said hotoxidant stream has a temperature higher than the temperature of saidregenerator flue gas and said residence time is short enough that saidhot oxidant stream contains products of said combustion includingradicals selected from the group consisting of radicals corresponding tothe formulas O, H, OH, C₂H, CH₂, C_(j)H_(2j+1) or C_(j)H_(2j-1) whereinj is 1-4, and mixtures of two or more of such radicals;

(C) feeding the hot oxidant stream into the regenerator flue gas streamto raise the temperature of the regenerator flue gas to a temperaturehigher than 1100 F that is higher than the temperature of the flue gasstream to which the hot oxidant stream is added, wherein the hot oxidantstream is added at a rate sufficient to convert carbon monoxide in theregenerator flue gas to carbon dioxide.

Another aspect of the invention is a method for treating a gas streamcomprising

(A) providing from a catalyst regenerator a regenerator flue gas streamthat contains carbon monoxide in a concentration less than 10,000 ppmand contains NOx in an amount up to 1,000 ppm;

(B) mixing fuel and oxygen and combusting a portion of the oxygen in themixture with said fuel in a first chamber to form a hot oxidant streamemerging from said first chamber that contains oxygen, wherein theresidence time of said combustion in said first chamber is long enoughthat said hot oxidant stream has a temperature higher than thetemperature of said regenerator flue gas and said residence time isshort enough that said hot oxidant stream contains products of saidcombustion including radicals selected from the group consisting ofradicals corresponding to the formulas O, H, OH, C₂H, CH₂, C_(j)H_(2j+1)or C_(j)H_(2j−1) wherein j is 1-4, and mixtures of two or more of suchradicals;

(C) feeding the first hot oxidant stream into the regenerator flue gasstream to raise the temperature of the regenerator flue gas to atemperature higher than the temperature of the flue gas stream to whichthe first hot oxidant stream is added, wherein the first hot oxidantstream is added at a rate sufficient to convert carbon monoxide in theregenerator flue gas to carbon dioxide;

(D) mixing fuel and oxygen and combusting a portion of the oxygen in themixture with said fuel in a second chamber to form a second hot oxidantstream emerging from said second chamber that contains oxygen, whereinthe residence time of said combustion in said second chamber is highenough that said second hot oxidant stream has a temperature that ishigher than the temperature of the regenerator flue gas stream intowhich said second hot oxidant stream is fed in step (E) and saidresidence time is low enough that said second hot oxidant streamcontains products of said combustion radicals selected from the groupconsisting of radicals corresponding to the formulas O, H, OH, C₂H, CH₂,C_(j)H_(2j+1) or C_(j)H_(2j−1) wherein j is 1-4, and mixtures of two ormore of such radicals;

(E) feeding the second hot oxidant stream into the regenerator flue gasstream downstream from the first hot oxidant stream to raise thetemperature of the regenerator flue gas to a temperature that is higherthan the temperature of the flue gas stream to which the second hotoxidant stream is added, wherein the second hot oxidant stream is addedat a rate sufficient to convert carbon monoxide in the regenerator fluegas to carbon dioxide.

Preferably, when the mixture is formed in step (C) catalyst is not addedthat would promote the conversion of the carbon monoxide or of the NOx.

As used herein, the term “NOx” means compounds of nitrogen and oxygen,and mixtures thereof, including but not limited to NO, N₂O, NO₂, N₂O₄,and mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowsheet showing a typical catalyst regeneration system inwhich present invention can be practiced.

FIG. 2 is a schematic representation of a hot oxygen generator useful inthe present invention.

FIG. 3 is a cross-sectional view of a hot oxygen generator useful in thepresent invention.

FIG. 4 is a flowsheet of a portion of an alternate embodiment of thepresent invention.

FIG. 5 is a flowsheet of yet another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

While the following description of the present invention refers to theFigures, the invention is not to be considered to be confined to theembodiments illustrated in the Figures.

Referring to FIG. 1, a FCC regenerator (10) receives and regeneratesused catalyst (2) from a FCC unit (not shown) and the regeneratedcatalyst (4) is mixed with a FCC feed stream (6) to form stream (8)which is transported back to the FCC unit. Regenerator flue gas stream(12) from regenerator (10) preferably passes through a device to removeentrained catalyst from the flue gas. One such device is cycloneseparator (20), wherein fine catalyst carried over by the flue gasstream (12) is separated and discharged through a conduit (22). Theregenerator flue gas stream (12) optionally but preferably goes througha power recovery turbine (23) to convert kinetic energy of theregenerator flue gas to readily usable power. After passing through thepower recovery turbine, the regenerator flue gas stream (12) flows intoand through a regenerator flue gas duct (30) or chamber, from which theflue gas (12) can pass into a downstream heat recovery unit (50) such asa heat exchanger.

As the FCC regenerator (10) is operated in the full burn mode, theregenerator flue gas stream (12) contains CO in an amount up to 5000 ppmand even up to 10,000 ppm, and contains NOx typically in amounts up to200 ppm and even up to 1,000 ppm of NOx.

In any of these modes, the regenerator flue gas stream entering duct(30) typically has a temperature ranging from 900 F, or from 1000 F or1100 F, and often up to 1600 F or up to 1800 F. The regenerator flue gastemperature can be up to 2600 F if appropriate measures are taken toaccommodate such high temperatures, such as using refractory materialsfor the duct construction and/or incorporating a way to carry heat awaysuch as a water wall in which heat passes through the duct wall and iscarried away by a stream of water.

In the regenerator flue gas duct (30), or in any suitable chamberinstead of a duct, a stream (32) of gaseous hot oxidant describedfurther herein is fed at high momentum into the regenerator flue gas.The desired reaction of the hot oxygen with the regenerator flue gas isenhanced by increasing the intimacy of mixing between the hot oxygen andthe flue gas. The intimate mixing can be promoted by dividing the hotoxygen into a plurality of streams and feeding these streams into theregenerator flue gas, or by feeding the hot oxygen across orcountercurrent to the flue gas. Preferably, the intimate mixing ispromoted by providing physical structure within duct or chamber (30)that promotes contact between the hot oxygen and the flue gas. Examplesof such structure include wire mesh that the gases have to flow through,or baffles. The hot oxidant and the regenerator flue gas mix, duringwhich the hot oxygen burns CO in the regenerator flue gas to CO₂ and mayalso convert at least some NOx present to environmentally benign N₂. Theresulting gas mixture as stream (38) comprises the products of thesereactions between the hot oxidant and the FCC regenerator flue gas andis available for further exploitation or for venting to the atmosphere.

If desired, optional separate oxidant stream 56 having an oxygenconcentration of at least 20.9 vol. % at ambient temperature, or heatedto above ambient temperature, can be fed into the regenerator flue gasupstream of where the hot oxidant stream is fed into the regeneratorflue gas.

In a preferred manner of exploiting stream (38), it is fed to heatrecovery unit (50) where it is cooled by indirect heat exchange toanother process stream. The flue gas stream, now shown as stream (58),after any such heat exchange, flows to a particulate-removal unit (60)such as an electrostatic precipitator. The gas stream then passesthrough a unit (70) such as a scrubber or for additional emissionscontrol and finally, the cleaned flue gas is sent to a stack (80) andemitted as stream (82) to the atmosphere. Other ways in which all or aportion of stream (38) can be exploited include using it as a feedstream for chemical process reactions, or combining it with anotherprocess stream for further treatment or use.

To provide the high momentum hot oxygen stream (32), referring now toFIG. 2, stream (40) of oxidant having an oxygen concentration of atleast 30 volume percent and preferably at least 85 volume percent isprovided into a hot oxygen generator (42) which is preferably a chamberor duct which communicates with the regenerator flue gas duct or chamberthrough a suitable passageway from an opening in generator (42). Mostpreferably the oxidant (40) is technically pure oxygen having an oxygenconcentration of 99.5 volume percent or more. The oxidant (40) fed tothe hot oxygen generator has an initial velocity which is generallywithin the range of from 50 to 300 feet per second (fps) and typicallywill be less than 200 fps.

Stream (44) of fuel is provided to the hot oxygen generator (42) througha suitable fuel nozzle which may be any suitable nozzle generally usedfor fuel injection. The fuel may be any suitable combustible fluidexamples of which include natural gas, methane, propane, hydrogen,refinery fuel gas, landfill offgas, syngas, carbon monoxide, and cokeoven gas. The presence of hydrogen in the fuel fed to the hot oxygengenerator (42) is advantageous in assisting conversion of CO to CO₂evidently because the combustion that forms the hot oxygen streampromotes the formation of (nonionic) OH and O radicals in the hot oxygenstream. Preferably the fuel is a gaseous fuel. Liquid fuels such asnumber 2 fuel oil may also be used, although it would be harder tomaintain good mixing and reliable and safe combustion with the oxidantwith a liquid fuel than with a gaseous fuel.

The fuel (44) provided into the hot oxygen generator (42) combusts therewith oxidant to produce heat and combustion reaction products such ascarbon dioxide and water vapor. Preferably, no more than about 35percent of the oxygen of the oxidant combusts with the fuel. If morethan about 35 percent of the oxygen combusts with the fuel in the hotoxygen generator, then appropriate measures should be taken such asusing refractory materials of construction and/or employing a heatremoval feature such as a water wall to keep the temperature of theremaining oxygen from increasing to undesirable levels.

The combustion reaction products generated in the hot oxygen generator(42) may mix with some of the remaining oxygen of the oxidant (40), thusproviding heat to some of the remaining oxygen and raising itstemperature. Preferably, the fuel is provided into the hot oxygengenerator (42) at a high velocity, typically greater than 200 fps andgenerally within the range of from 500 to 1500 fps. The high velocityserves to entrain oxidant into the combustion reaction products thuspromoting combustion of the fuel in the chamber.

Generally the temperature of remaining oxidant within the oxidant supplyduct is raised by at least about 500 F, and preferably by at least about1000 F. It is preferred however that the temperature of the remainingoxidant not exceed about 3000 F to avoid overheating problems withsupply ducts and nozzles.

As the temperature of the remaining oxygen within the hot oxygengenerator (42) is increased, the requisite supply pressure of theoxidant to achieve any given oxidant injection velocity into theregenerator flue gas decreases. For example, for injection of the oxygenat ambient temperature the requisite pressure exceeds 7 pounds persquare inch gauge (psig) in order to inject the oxygen into theregenerator flue gas at a velocity of 800 fps. As the oxygen temperatureincreases, the requisite pressure decreases sharply. At a temperature of1500 F the requisite pressure is 1.65 psig and at a temperature of 3000F the requisite pressure is only 0.91 psig. At temperatures exceeding3000 F there is little additional benefit, thus providing another reasonfor not exceeding 35 percent oxygen combustion with the fuel. Thus,generation of hot oxygen in this manner can provide a high velocity hotoxygen stream (32) to the regenerator flue gas without the need for ahigh supply pressure thus reducing or eliminating the need forcompressing oxidant prior to passing it into the regenerator flue gaswhich would otherwise be necessary if the oxidant source pressure is nothigh.

The combustion that occurs in hot oxygen generator (42) should becarried out in a manner such that the hot oxygen stream (32) thatemerges from generator (42) contains one or more radicals correspondingto the formulas O, H, OH, C₂H, CH₂, C_(j)H_(2j+1) or C_(j)H_(2j−1)wherein j is 1-4, and mixtures of two or more of such radicals. This canbe achieved by providing that the residence time of the reactants (fueland oxygen) within hot oxygen generator (42) is long enough to enablecombustion reaction of fuel and oxygen to occur in the hot oxygengenerator (42) producing a stream having a temperature higher than thetemperature of the regenerator flue gas into which the stream is to befed, and simultaneously providing that said residence time is shortenough that at least some of the above-mentioned radicals are present.The residence time, in turn, is determined by the volume of the spacewithin generator (42), by the feed rates of fuel stream (44) and ofoxidant stream (40) into generator (42), and by the size of the exitorifice through which the hot oxygen stream (32) emerges from generator(42). Preferred residence times are about 1 to 2 msec.

The hot oxygen stream (32) that is fed into the regenerator flue gasstream (12) may also lower the amount of NOx that is in the regeneratorflue gas.

Referring to FIG. 3, a cross-section of a hot oxygen generator (42) isshown. Fuel (44) emerges from orifice (45) whose diameter is “X”. Oxygenstream (40) flows in front of orifice (45) and combusts with the fuel.The resulting hot oxygen stream (32) emerges from generator (42) throughorifice (41), whose diameter is “Y”. The distance from orifice (45) toorifice (41) is “Z”. In general, the combination of the dimensions of ahot oxygen generator, the fuel and oxygen feed rates to that generator,and the exit orifice dimensions, that provide residence time which canproduce a hot oxygen stream that has the desired temperature and thedesired content of combustion radicals so as to reduce the CO contentand reduce or maintain the NOx content of a flue gas stream into whichthe hot oxygen stream is fed, includes the following:

X: 0.3-1.0 mm Y: 1.5-2.65 mm

Z: 1.0-3.5 inchesFuel (natural gas) feed rate into the generator: 2-14 scfhOxygen feed rate into the generator: 16-72 scfhPressure within the generator: 15.1-67.8 psia

The hot oxygen stream (32) preferably contains at least 75% (volume) O₂.A typical composition for this stream is about 80% O₂, 12% H₂O, 6% CO₂,some highly reactive radicals such as (nonionic) OH, O, and H which areparticularly effective to initiate and oxidize CO to CO₂, and theaforementioned hydrocarbon radicals which promote reactions that lowerthe amount of NOx present. The hot oxygen stream (32) exits throughorifice (41) and is fed to the regenerator flue gas at high velocity andmomentum, which results in accelerated mixing between the hot gas andthe FCC regenerator flue gas.

The hot oxygen stream (32) obtained in this way typically has atemperature of at least 1600 F and preferably at least 2000 F. Generallythe velocity of the hot oxygen stream will be within the range of from500 to 4500 feet per second (fps), preferably 800 to 2000 or to 2500fps, and will exceed the initial velocity by at least 300 fps. In apreferred embodiment this velocity is at Mach 1.

The description in U.S. Pat. No. 5,266,024, the content of which ishereby incorporated herein by reference, further describes formation ofthe high momentum hot oxygen stream.

The high velocity hot oxygen stream is believed to entrain the FCCregenerator flue gas (12) through jet boundaries by velocity gradientsor fluid shear, and by turbulent jet mixing. The gaseous stream that isformed upon combining the regenerator flue gas and the hot oxygenstream, which mixture may include reaction products of the hot oxygenand the regenerator flue gas, has a temperature of at least 1000 F,preferably at least 1250 F, although advantages can be realized when thetemperature of this mixture is above 1400F.

In other embodiments of the invention, two or more high momentum hotoxidant streams are fed into the regenerator flue gas stream. FIG. 4illustrates one such embodiment. In FIG. 4, FCC regenerator flue gasstream (12) enters duct (30) where it mixes with a high momentum hotoxidant stream (32) formed and fed as described above with respect tostream (32) in FIG. 1. Part of the CO and NOx contained in theregenerator flue gas stream (12) are destroyed during this mixing,forming reacted mixture stream (31) into which a second high momentumhot oxidant stream (33) is fed and mixes. Stream (33) is formed and fedas described above with respect to stream (32), and has the same ordifferent composition as stream (32). The second stream (33) mixes withthe reacted mixture stream (31) and further lowers the amount of CO, andNOx in stream (31). The resulting mixture stream (38) can then betreated or used as described above.

In this embodiment, the conversion of CO in the regenerator flue gas toCO₂ will occur under less oxidizing conditions in multiple stagesbecause the hot oxygen is supplied not all at once. Under thisconfiguration, the NOx destruction reactions occur in longer residencetimes under these less oxidizing conditions because of the stagedburnout of the CO. Therefore, higher destruction efficiencies of NOx areexpected.

FIG. 5 shows yet another embodiment of this invention. In FIG. 5, highmomentum hot oxidant stream (32) is fed into the regenerator flue gasstream after cyclone separator (20) and upstream from power recoveryturbine (23). In this embodiment, the heat provided by the hot oxygenand the heat released by the CO burnout can increase the regeneratorflue gas temperature by 70 F to 90 F, before the gas stream enters thepower recovery turbine (23). The feeding of the hot oxygen stream (32)for CO burnout also increases the total regenerator flue gas mass flowby about 0.6% to 2%. The increased mass flow and gas temperature wouldincrease the output of the power recovery turbine due to the increase ofthe gas stream's momentum entering the turbine. The amount of the hotoxygen flow and the extent of the CO burnout can be controlled to meetthe turbine's temperature limits.

Other combinations of configurations exist. For example, an optionalsecond high momentum stream of hot oxidant (32 b) could be fed after theturbine (23). In this case, the burnout of the CO is staged. Thedestruction efficiency of the NOx is expected to be higher. Also, two ormore hot oxygen streams can be formed and fed in parallel into theregenerator flue gas.

When a carbon monoxide boiler is present, operational limits on the COboiler are eased or removed. That is, the upstream FCC unit may operateat lower excess oxygen, for capacity increase, i.e., the feed rate tothe FCC is increased while the air flow rate is kept at an allowablemaximum. Under this operating condition, the FCC regenerator flue gaswill contain more CO and may contain some NOx. However, this FCCregenerator flue gas will mix rapidly with the injected high-momentumhot oxygen for both CO burnout and NOx destruction. The amount of thehot oxygen injected can be tailored so that increased amounts of CO andNOx in the regenerator flue gas can be destroyed. In essence, thisinvention removes limitations imposed by the overall FCC regenerationoperations in handling regenerator flue gas containing higherconcentrations of CO and NOx. Thus, the invention allows existing FCCunits to operate at higher capacities with little capital investment.

This invention is also surprising given that combustion reactions withoxygen and higher temperatures such as are employed herein are oftenassociated with increased production of NOx beyond the levels ofproduction encountered here. Also, the invention is expected to have thefollowing unique and unobvious advantages:

The injection of the hot oxygen can have synergistic effect in boostingthe output of a power recovery turbine. That is, when a high momentum,hot oxidant stream is fed into the regenerator flue gas stream upstreamof the power recovery turbine, the heat provided by the hot oxygen andthe heat released by the CO burnout can increase the regenerator fluegas temperature. The injection of the hot oxygen for CO burnout alsoincreases the total regenerator flue gas mass flow. The increased massflow and gas temperature would increase the output of the power recoveryturbine due to the increase of the gas stream's momentum entering theturbine.

Also, consumption of CO combustion promoters in the regenerator isreduced or eliminated. That is, many FCC regenerators use platinum-basedCO combustion promoters to accelerate CO burnout for controlling COafterburn. It has been reported that the use of the platinum-basedcombustion promoters increases NOx concentration in the regenerator fluegas. Hence, the amount of CO reduction must be balanced with the maximumamount of NOx allowed, through the amount of combustion promoters usedin the regenerator bed. The combustion promoters may not be reclaimedentirely so there are economic losses associated with the loss of theexpensive combustion promoters. If a high momentum hot oxygen stream isfed into the regenerator flue gas stream as described herein, the amountof these combustion promoters in use may be reduced. This is because thehot oxygen can destroy the CO in the downstream regenerator flue gas.The reduced consumption of combustion promoters will in turn decreasethe amount of unrecoverable promoters thus reducing the operating costsof a FCC unit.

The invention is further illustrated in the following example.

EXAMPLE

Various gas mixtures, representing simulated flue gases, were preparedand a hot oxygen stream was generated and fed into the gas mixturesunder various conditions. Table 1 below sets forth the temperature, theCO concentration, the concentration of nitrogen oxides, the oxygenconcentration, and the carbon dioxide concentration, for each gasmixture tested, both before and after a hot oxygen stream was fed intothe gas mixture. Each gas mixture into which a hot oxygen stream was fedcontained 9 vol. % H2O, 11 vol. % CO2, 80 vol. % N2, as well as CO andNOx in the concentrations stated in Table 1. Several different exitnozzles of the hot oxygen generator were tested as well. Table 1 alsoindicates which nozzle was used in each test. Table 2 indicates therange of operating conditions and the different exit nozzle sizes forthe hot oxygen generator.

TABLE 1 Test Results Flue gas in: Nozzle Type Flue gas out: CaseTemperature CO NOx O2 CO2 [—] Temperature CO NOx O2 CO2 CO change NOxchange No. (F.) (ppm) (ppm) (%) (%) [—] (F.) (ppm) (ppm) (%) (%) % % 11202 4636 27 0 10.0 A 1373 73 40 1.41 11.1 −98.4 46.5 2 1204 4171 27 010.3 B 1369 85 32 1.39 11.3 −98.0 15.8 3 1201 3760 26 0 10.1 C 1299 39728 0.95 10.9 −89.4 5.4 4 1203 4166 30 0 10.7 D 1331 171 33 1.21 11.6−95.9 10.5 5 1204 3908 28 0 10.2 E 1366 61 29 0.75 11.3 −98.4 2.9 6 12554109 39 0 10.1 A 1370 45 49 1.15 11.0 −98.9 27.1 7 1255 4371 36 0 10.1 B1374 68 35 2.30 11.0 −98.4 −2.8 8 1253 4076 36 0 10.2 E 1372 68 31 2.2811.0 −98.3 −12.9 9 1249 4582 120 0 10.7 E 1385 38 109 1.25 11.6 −99.2−8.7 10 1248 548 124 0 10.2 E 1330 59 117 1.45 10.6 −89.2 −5.8 11 13083645 35 0 10.5 C 1385 80 58 2.70 11.1 −97.8 65.5 12 1407 3822 64 0 10.9E 1429 21 60 0.91 11.5 −99.5 −6.4Gas compositions listed in the table are based on dry gaseous volume.

TABLE 2 Hot-Oxygen Generator Operating Conditions and Dimensions (Ref.to FIG. 3 for definition) Case Fuel flow Oxyegn flow Pressure NozzleType X Y Z No. (scfh) (scfh) (psia) [—] (mm) (mm) (inches) 1 11.9 47.815.2 A 1.00 5.00 1.04 2 12.0 48.0 15.3 B 1.00 5.00 2.04 3 7.9 32.3 40.9C 0.30 1.50 1.29 4 9.9 39.8 20.8 D 1.00 2.65 2.54 5 12.1 36.0 19.1 E1.00 2.65 1.29 6 9.0 36.0 15.1 A 1.00 5.00 1.04 7 10.0 59.9 15.4 B 1.005.00 2.04 8 10.0 59.9 20.8 E 1.00 2.65 1.29 9 12.2 48.7 20.4 E 1.00 2.651.29 10 12.1 48.2 20.2 E 1.00 2.65 1.29 11 5.6 59.2 67.8 C 0.30 1.501.29 12 5.0 30.6 16.7 E 1.00 2.65 1.29

The total flue gas flow used in the example experiment was approximately2200 scfh. Fuel flow to the hot oxygen generator varied in a rangebetween 5.0 scfh to 12.2 scfh, and the corresponding oxygen flow to thehot oxygen generator changed between 30.6 scfh to 60.0 scfh. Fuel nozzlesize varied between 0.3 mm to 1.0 mm for the five nozzles indicated inTable 1, and the size of the exit hot oxygen nozzle varied between 1.5mm to 5 mm. The fuel nozzle was recessed from the oxygen nozzle at adistance between 1.04 inches to 2.54 inches. The operating pressure ofthe hot oxygen generator was between 15.1 psia to 67.8 psia.

The temperature of the regenerator flue gas for Case 1 was 1202 F, and anozzle design “A” was selected for the hot oxygen generator. Before thehot oxygen injection, the flue gas contained 4636 ppm of CO, 27 ppm ofNOx, little or no oxygen, and 10% of CO2. Downstream after the hotoxygen injection, the temperature of the flue increased to 1373 Fbecause the injected oxygen was hot and also due to the release of thechemical heat from CO oxidation to CO2. CO reduced to 73 ppm (i.e., a98.4% reduction) and in this case NOx increased to 40 ppm (i.e., a 46.5%increase). The excess oxygen was 1.41% after the hot oxygen injection.

Cases 2 to 5 used different nozzle designs (i.e., nozzles “B”, “C”, “D”,and “E”, respectively) to reduce CO, while attempting to keep the fluegas temperatures and CO concentrations before the hot oxygen injectionas close as possible to those values of the Case 1. It can be seen thatnozzle “E” of Case 5 was a better design for the application, because itdestroyed CO from 3908 ppm to 61 ppm, while at the same time keeping theNOx level almost constant from 28 ppm at the inlet to 29 ppm at theoutlet.

Cases 6 to 10 were carried out at higher flue gas inlet temperaturesbetween 1248 F to 1255 F. Nozzle “E” was shown, again, to have the bestNOx performance. For instance, Case 8 demonstrated that nozzle “E”reduced CO from 4076 ppm to 68 ppm, while simultaneously minimized theflue gas NOx from 36 ppm to 31 ppm. The NOx reduction capability ofnozzle “E” was further confirmed in Cases 9 and 10 where flue gas inletNOx and inlet CO concentrations were varied. In Case 9 NOx concentrationat the flue gas inlet was higher at 120 ppm, and in Case 10 COconcentration at the flue gas inlet was lower at 548 ppm. In both Cases,the hot oxygen streams from nozzle “E” destroyed the flue gas inlet COand simultaneously reduced the inlet NOx by 8.7% and 5.8%, respectively.

Cases 11 and 12 were carried out at inlet flue gas temperatures evenhigher at 1308 F and 1407 F, respectively. In Case 11, nozzle “C” wasused but NOx increased from 35 ppm before the hot oxygen injection to 58ppm after the injection. The NOx reduction ability of nozzle “E” wasdemonstrated again in Case 12, where the inlet flue gas temperature wasthe highest at 1407 F. It can be seen that nozzle “E” of Case 12destroyed CO from 3822 ppm to 21 ppm, while at the same time reduced theNOx from 64 ppm at the inlet to 60 ppm at the outlet.

1. A method for treating a regenerator flue gas stream comprising (A)providing from a catalyst regenerator a regenerator flue gas stream thatcontains carbon monoxide in a concentration less than 10,000 ppm andcontains NOx in an amount up to 1,000 ppm; (B) mixing fuel and oxygenand combusting a portion of the oxygen in the mixture with said fuel ina chamber to form a hot oxidant stream emerging from said chamber thatcontains oxygen, wherein the residence time of said combustion in saidchamber is long enough that said hot oxidant stream has a temperaturehigher than the temperature of said regenerator flue gas and saidresidence time is short enough that said hot oxidant stream containsproducts of said combustion including radicals selected from the groupconsisting of radicals corresponding to the formulas O, H, OH, C₂H, CH₂,C_(j)H_(2j+1) or C_(j)H_(2j−1) wherein j is 1-4, and mixtures of two ormore of such radicals; (C) feeding the hot oxidant stream into theregenerator flue gas stream to raise the temperature of the regeneratorflue gas to a temperature higher than 1100 F that is higher than thetemperature of the flue gas stream to which the hot oxidant stream isadded, wherein the hot oxidant stream is added at a rate sufficient toconvert carbon monoxide in the regenerator flue gas to carbon dioxide.2. A method according to claim 1 wherein the temperature of theregenerator flue gas stream that is provided in step (A) is up to 1800F.
 3. A method according to claim 1 wherein the stream that is formed instep (C) by feeding the hot oxidant stream into the regenerator flue gashas a temperature of at least 1250 F.
 4. A method according to claim 1wherein the stream that is formed in step (C) by feeding the hot oxidantstream into the regenerator flue gas has a temperature of at least 1400F.
 5. A method according to claim 1 wherein no more than 35% of theoxygen mixed with fuel in step (B) is combusted in step (B).
 6. A methodaccording to claim 1 wherein the hot oxidant stream formed in step (B)is fed into the regenerator flue gas stream in step (C) at a velocity ofat least 500 feet per second.
 7. A method according to claim 1 whereinthe hot oxidant stream formed in step (B) is fed into the regeneratorflue gas stream in step (C) at a velocity of Mach
 1. 8. A methodaccording to claim 1 wherein the regenerator flue gas stream is passedthrough a power recovery turbine before the hot oxidant stream is fedinto it in step (C).
 9. A method according to claim 1 wherein NOx in theregenerator flue gas is converted to N₂ wherein the amount of NOx in theproduct stream following said conversion is not greater than the amountof NOx in said regenerator flue gas stream before said mixture isformed.
 10. A method for treating a regenerator flue gas streamcomprising (A) providing from a catalyst regenerator a regenerator fluegas stream that contains carbon monoxide in a concentration less than10,000 ppm and contains NOx in an amount up to 1,000 ppm; (B) mixingfuel and oxygen and combusting a portion of the oxygen in the mixturewith said fuel in a first chamber to form a hot oxidant stream emergingfrom said first chamber that contains oxygen, wherein the residence timeof said combustion in said first chamber is long enough that said hotoxidant stream has a temperature higher than the temperature of saidregenerator flue gas and said residence time is short enough that saidhot oxidant stream contains products of said combustion includingradicals selected from the group consisting of radicals corresponding tothe formulas O, H, OH, C₂H, CH₂, C_(j)H_(2j+1) or C_(j)H_(2j−1) whereinj is 1-4, and mixtures of two or more of such radicals; (C) feeding thefirst hot oxidant stream into the regenerator flue gas stream to raisethe temperature of the regenerator flue gas to a temperature higher thanthe temperature of the flue gas stream to which the first hot oxidantstream is added, wherein the first hot oxidant stream is added at a ratesufficient to convert carbon monoxide in the regenerator flue gas tocarbon dioxide; (D) mixing fuel and oxygen and combusting a portion ofthe oxygen in the mixture with said fuel in a second chamber to form asecond hot oxidant stream emerging from said second chamber thatcontains oxygen, wherein the residence time of said combustion in saidsecond chamber is high enough that said second hot oxidant stream has atemperature that is higher than the temperature of the regenerator fluegas stream into which said second hot oxidant stream is fed in step (E)and said residence time is low enough that said second hot oxidantstream contains products of said combustion radicals selected from thegroup consisting of radicals corresponding to the formulas O, H, OH,C₂H, CH₂, C_(j)H_(2j+1) or C_(j)H_(2j−1) wherein j is 1-4, and mixturesof two or more of such radicals; (E) feeding the second hot oxidantstream into the regenerator flue gas stream downstream from the firsthot oxidant stream to raise the temperature of the regenerator flue gasto a temperature that is higher than the temperature of the flue gasstream to which the second hot oxidant stream is added, wherein thesecond hot oxidant stream is added at a rate sufficient to convertcarbon monoxide in the regenerator flue gas to carbon dioxide.
 11. Amethod according to claim 10 wherein the temperature of the regeneratorflue gas stream that is provided in step (A) is up to 1800 F.
 12. Amethod according to claim 10 wherein the stream that is formed in step(C) by feeding the hot oxidant stream into the regenerator flue gas hasa temperature of at least 1250 F.
 13. A method according to claim 10wherein the stream that is formed in step (C) by feeding the hot oxidantstream into the regenerator flue gas has a temperature of at least 1400F.
 14. A method according to claim 10 wherein no more than 35% of theoxygen mixed with fuel in step (B) is combusted in step (B).
 15. Amethod according to claim 10 wherein no more than 35% of the oxygenmixed with fuel in step (D) is combusted in step (D).
 16. A methodaccording to claim 10 wherein the hot oxidant stream formed in step (B)is fed into the regenerator flue gas stream in step (C) at a velocity ofat least 500 feet per second.
 17. A method according to claim 10 whereinthe hot oxidant stream formed in step (D) is fed into the streamproduced in step (C) at a velocity of at least 500 feet per second. 18.A method according to claim 10 wherein NOx in the regenerator flue gasis converted to N₂ whereby the product stream of step (E) comprises N₂.19. A method according to claim 10 wherein the hot oxidant stream formedin step (B) is fed into the regenerator flue gas stream in step (C) at avelocity of Mach
 1. 20. A method according to claim 10 wherein the hotoxidant stream formed in step (D) is fed into the stream produced instep (C) at a velocity of Mach
 1. 21. A method according to claim 19wherein the hot oxidant stream formed in step (D) is fed into the streamproduced in step (C) at a velocity of Mach
 1. 22. A method for treatinga gas stream comprising (A) providing a gas stream that contains watervapor, carbon dioxide, N₂, carbon monoxide in a concentration less than10,000 ppm, and NOx in an amount of up to 1,000 ppm; (B) mixing fuel andoxygen and combusting a portion of the oxygen in the mixture with saidfuel in a chamber to form a hot oxidant stream emerging from saidchamber that contains oxygen, wherein the residence time of saidcombustion in said chamber is long enough that said hot oxidant streamhas a temperature higher than the temperature of said gas stream andsaid residence time is short enough that said hot oxidant streamcontains products of said combustion including radicals selected fromthe group consisting of radicals corresponding to the formulas O, H, OH,C₂H, CH₂, C_(j)H_(2j+1) or C_(j)H_(2j−1) wherein j is 1-4, and mixturesof two or more of such radicals; (C) feeding the hot oxidant stream intothe gas stream provided in step (A) to raise the temperature of said gasto a temperature higher than 1100 F that is higher than the temperatureof the gas stream to which the hot oxidant stream is added, wherein thehot oxidant stream is added at a rate sufficient to convert carbonmonoxide in the gas to carbon dioxide.
 23. A method according to claim22 wherein the temperature of the gas stream that is provided in step(A) is up to 1800 F.
 24. A method according to claim 22 wherein thestream that is formed in step (C) by feeding the hot oxidant stream intothe regenerator flue gas has a temperature of at least 1250 F.
 25. Amethod according to claim 22 wherein the stream that is formed in step(C) by feeding the hot oxidant stream into the regenerator flue gas hasa temperature of at least 1400 F.
 26. A method according to claim 22wherein no more than 35% of the oxygen mixed with fuel in step (B) iscombusted in step (B).
 27. A method according to claim 22 wherein thehot oxidant stream formed in step (B) is fed into the gas stream in step(C) at a velocity of at least 500 feet per second.
 28. A methodaccording to claim 22 wherein the hot oxidant stream formed in step (B)is fed into the gas stream in step (C) at a velocity of Mach
 1. 29. Amethod according to claim 22 wherein NOx in the gas stream is convertedto N₂ thereby producing a product stream wherein the amount of NOx inthe product stream following said conversion is not greater than theamount of NOx in said gas stream before said mixture is formed.